206 MASS. EXPERIMENT STATION BULLETIN 170. 



Winterkilling of Cork Cambium. 

 As already stated, the effects of low temperature on a tree may be en- 

 tirely local; i.e., it may affect some particular organ or some one portion 



% 

 % 



75 

 70 

 65 



40-6096 



50" 

 Iff 



'0* '"1 i'"" , , 



0° 



1.1 II 



n 



30.5..., 

 5Q0 Li" 

 29.5 



29.0 m 



55 

 50 

 25 



20 



MEAN REL HUMIDITY 



'5 H^EAN TEMP 



BAROMETER 



FROST CRACK 



5 



Fitj. 79. — Showing curve of opening and closing of frost cracljs in elm trees. The 

 lower curve i-epresents the variations in the opening and closing the others 

 represent the mean relative luimidity, mean temperature and barometer in 

 the order named. 



of the tree only. Following one of our extremely severe winters a few 

 years ago, elms and some sycamores were found suddenly discarding 

 their outer bark, — a rather unusual phenomenon. This loss of the outer 



